黑马day11 c3p0数据库连接池

c3p0数据库连接池：我们以后开发就使用这个数据库连接池，非常的方便。只需要一个配置文件即可，c3p0默认是在类字节码文件中找到c3p0-config.xml文件。

使用步骤：

1.导入相应的jar包即可

2.然后再类中使用

案例1：

package com.itheima.c3p0;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0Demo1 {
	public static void main(String[] args) {
		Connection con = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try{
			//方式1:
			ComboPooledDataSource dataSource=new ComboPooledDataSource();
			dataSource.setDriverClass("com.mysql.jdbc.Driver");
			dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/day11");
			dataSource.setUser("root");
			dataSource.setPassword("169500");
			con=dataSource.getConnection();
			ps = con.prepareStatement("select * from account");
			rs = ps.executeQuery();
			while (rs.next()) {
				String name = rs.getString("name");
				System.out.println(name);
			}
		} catch (Exception e) {
			e.printStackTrace();
			throw new RuntimeException();
		} finally {
			if (rs != null) {
				try {
					rs.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					rs = null;
				}
			}
			if (ps != null) {
				try {
					ps.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					ps = null;
				}
			}
			if (con != null) {
				try {
					con.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					con = null;
				}
			}
		}

	}
}

方式二：在src目录下建立一个配置文件名为c3p0-config.xml文件，使用c3p0数据库连接池的类会自动找到在类字节码文件的这个配置文件：

配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
  <default-config>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/day11</property>
    <property name="user">root</property>
    <property name="password">169500</property>
  </default-config>

</c3p0-config>

在类中使用：

package com.itheima.c3p0;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0Demo2 {
	public static void main(String[] args) {
		Connection con = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try{
			//方式1:
			ComboPooledDataSource dataSource=new ComboPooledDataSource();//会默认寻找配置文件
			con=dataSource.getConnection();
			ps = con.prepareStatement("select * from account");
			rs = ps.executeQuery();
			while (rs.next()) {
				String name = rs.getString("name");
				System.out.println(name);
			}
		} catch (Exception e) {
			e.printStackTrace();
			throw new RuntimeException();
		} finally {
			if (rs != null) {
				try {
					rs.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					rs = null;
				}
			}
			if (ps != null) {
				try {
					ps.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					ps = null;
				}
			}
			if (con != null) {
				try {
					con.close();
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					con = null;
				}
			}
		}

	}
}

运行结果：

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